<script type="text/javascript">
function changeHiddenData(){
    $("#testdata").val("changed");
}
</script>


<form action="/default/hiddencng" method="get" id="latlng" name="latlng">
<input type="hidden" name="testdata" id="testdata" value="hgoe">
<input type="submit">
</form>

<input type="button" value="change" onClick="javascript:changeHiddenData()">

<?php echo $testdata?>


